Facilitate generic programming with overloaded operators about nalgebra HOT 2 CLOSED

I think the current support of multidispatch by rustc can give us just enough flexibility to fix this easily using something like this:

impl<N: Mul<N, N>> Vec2MulRhs<N, Vec2<N>> for N {
    #[inline]
    fn binop(left: &Vec2<N>, right: &N) -> Vec2<N> {
        Vec2::new(left.x * *right, left.y * *right)
    }
}

In fact I believe the only thing that prevents us from using multidispatch only instead of the double-dispatch trick are some corner-cases I encountered in ncollide that require better where clauses (though those corner cases might be related to the current issue and be fixed at the same time as this, I have to check).

from nalgebra.

The problem with that is just that you can't have multiple generic implementations, which would prevent Matrix * Vector and Matrix * Scalar to be implemented at the same time like this.

Maybe we could do something like this:

trait DDMul<C> {
    fn ddmul(&self) -> C;
}

impl<T: BaseFloat> DDMul<Vec2<T>> for (Vec2<T>, T) { /* ... */ }

impl<B, C> Mul<B, C> for Vec2
    where (Vec2, B): DDMul<C>
{
    fn mul(&self, other: &B) -> C { (*self, *other).ddmul() }
}

But this is only useful for the brief period between full where clauses and multidispatch.

from nalgebra.